Process of crystallizing borax from solution



ROBERT 28. FEET, F TRONA, CALIFORNIA, Assrenon "r0 AMERICAN POTASH &

"No Drawing.

Patented Feb. 17-, 1931 r CHEMICAL CORPORATION, or TRONA, WARE ENT Q C w CALIFORNIA, A CORPORATION OF DELA- IROCESS or CnYs'rALLrzme BORAX FROM SOLUTION.

Application filed ril 16,

This invention relates to the production of single crystals of borax frcmconcentrated aqueous solutions at a rapid rate. f In par- .ticularthis invention relates to crystallization of boraX from essentially pure aqueous solutions, but. may be applicable to solutions of complex nature containing crystallizable quantities of boraxg i The usual method of crystallizing b orai is bycooling a hot concentrated solution. .In

many cases such a solution may result-from concentrationand manipulation .o f natural 11131118 3, such, for example, as .Searles Lake .orOWens Lake brine. However, 1t often occurs that an undesirable grade of boraxmay be obtained'from such a. source,-or directly from mineral deposits, Which must be dissolved andrecrystallized for the production of high grade borax. .The processof this invention is. useful in any of theseinst-ances,

' .and' it may bexapplied successfullyto the crystallization of borax. from: liquors produced by decompositlon ofcertam horate ores;

processofthis invention, I have rapidlypro- .duced satisfactorysingle crystals of refined boraX from a concentrated aqueous solution prepared from crude borax. This partlcular crude borax resultedfrom the evaporation,

manipulation and cooling of Searles Lake Due to the physical and chemical nature ofthe liquor and to the temperature of c0oling,'this crude borax was considered e 7 crystals of boraX, it has always been found unfit for commercial purposes, containing small amounts of arsenates, phosphates, chlorides, etc. of sodium and potassium together with considerable dirtf g I The crude borax as? described orally other undesirable; borax, is dissolvedin pure ater or n any suitable aqueous solvent, such .as cnd hquor from previous crystallization. of

.borax. ,flhe solution maybe treated with suitable reagents for the removal of undesirable impurities, and filt'eredmfor the re- .moval o't insoluble matter, such as dirt, etc. fTheresulting clear filtered liquor, which i should preferably be saturatedpwith bor ax 1 at a high temperature, is, then suitable for cooling for the precipitation of boraX, the

an of the application of the i929. serialno. 355s.

stepto which the present invention nent. p v

Cooling maybe brought about in any one of a number of Well known pieces of equipis pertiment suited tothat purpose. When such a solution is cooled to cause the borax present to crystalhze'out, n order to obtain a granular product which maybe removed sludge an d ivhich will not remain or the most part as a massive deposit adhering to the Walls and bottom of thecrystallizing vessel, some mechanical means'are usiially provided for the purpose of maintaining the growing crystals in suspensionin the mother liquor.

Due to various causes such'as surface tension eifects, electrostatic effects and accidental collisions, the suspended crystals tend tocome together too-form groups of two or- It is the primary object of. the present in lventlon to provide a process bywhich borax may be precipitated as crystals from a solution or. super-saturated solution of borax WlthOllt the crystals being successively clustered together :or cemented, but in place, to provlde a process in Which to a large extent,

the crystals of borax areobtained in the precipitating process as single crystals;

Heretofore in order to produce single necessary, to conduct the crystallizing procedure very slowlyin order that a high degree of supersaturation may not at any t me be attained. WVhen'thecooling is carried outslovvly, the, effects of mechanical agitadesirable that crystallization be-conducted as rapidly as possible in order to increase the ou'tput'oit the apparatus. Y

. It istherefore'a further object of em; invention to provide -a"proce'ss; of rapae asidly precipitating boraX as single crystals.

I have discovered that a highly super-saturated solution of bOliiX can be caused to precipitate boraX in single crystals rapidly, if there is added to the super-saturated solution at the start of the precipitation operations, a small amount of soap, fatty acid or other emulsion colloid of similar nature. The effect of the addition of soap is to prevent or suppress the aggregation of crystals to such an extent that although the crystallization may be conducted. rapidly, the product resulting will consist mainly of single crystals. 7

The particular phenomena responsible for the effects of the process of this invention are somewhat obscure and not entirely known. However, this may be due to the effects of adsorption of the added emulsion colloid on the surfaces of the crystal nuclei or seeds. It also may reside in the fact that due to the presence of the emulsion colloid, the surfaces of the crystals becomecharged electrically and therefore the different crystals or seeds, tend to repel each other. Also, it may be due to the fact that protective films of adsorbed material are produced on the surfaces of the crystals, which films tend to prevent diflerentcrystals from coming into a sufficiently intimate contact that a permanent union may be effected between the crystals.

The effect is not a simple viscosity effect since substances like sugar which mainly tend to increase the viscosity of the solution are apparently without effect insofar as the prevention of crystal aggregation is coucerned. Neither is it entirely an adsorption effect since many dyes and inorganic colloids are adsorbed by crystal surfaces, but here again there is no tendency towards the prevention of aggregation in the case of boraX. Apparently the adsorption of an organic'emulsion colloid is necessary, and a great variety of such colloids may be used and such colloids are also known as emulsoids, or lyophylic colloids.

The present invention, together with various additional objects and advantages thereof will best be understood from a description of the preferred form or example of a process embodying the invention. For this purpose I have hereafter described a prcferred form or example of such process.

Any hot concentrated aqueous solution of borax is suitable for the process of the present invention. Since the object of producing single crystals of good structure is largely for the satisfaction of the trade, it is desirable that the solution be as free from obectionable impurities as practicable. However, I have found that even higher impurities may be tolerated in the present mother liquor than in mother liquors of past practice; due to the fact that the processof this invention produces single crystals more easily freed from the adhering liquor than the complex aggregated crystals produced prior to the inception of this invention.

Under conditions of operation hereafter described I. employ a hot concentrated solution made from crude borax, Water and a certain amount of end liquor from previous crystallizations. The hot solution is filtered for theremoval of all solid foreign matter.

The borax solution thus obtainedor a borax solution obtained in any other desired or preferred manner is then preferably cooled. I prefer to-use a vacuum crystallizer in which the hot solutionis cooled rapidly by reducing the pressure on the solution, evaporating part of the solution so as to cool the solution due to the loss of heat by vaporization of water vaporized by the pressure reducing opera tion. The solution in the cooling chamber is agitated by mechanical or any other preferred means in order to cause an orderly ebu-llition and also to maintain the crystals in suspension.

As an example of the process, the process is carried on in batches of solutions of approximately 2500 gallons. The solution at the start, contains approximately 16% anhydrous boraX. (Na B O and is at a telnperature of about 80 C. The solution is cooled rapidly down to say 58 C. which is ap proximately 2 below thetemperatnre atwhich such a solution would be just saturated in the mother liquor. If such a solution is then inoculated with a few pounds of fine borax crystals in order to start crystallization and the cooling continued until a temperature of 35 C. is reached, the crystals of borax precipitated will consist almost entirely of complex aggregates.

In accordance with the process of the present invention, the solution, previous to inoculating with fine borax crystals, has added about one pound of common laundry soap dissolved in about ten gallons of hot water. The solution is then inoculated with a few pounds of line boraX crystals and cooled to b5 C. In this case the borax crystals produced are found to consist almost entirely of perfect single crystals of boraX.

Cooling, from 80 C. to 35 C. is accomplished in about two hours. However, the time ma y be varied from say one hour or less to four hours or m ore, according to the. size of crystal desired. The size of the resulting crystal borax is largely dependent upon the time and manner of cooling. Single crystals not only have the advantage of a pleasin'gappearance, but have also been found more susceptible to satisfactory separation, washing and drying operations. Likewise single crystals of borax. have a lesser tendency toward dehydration and caking in transit, than the irregular, broken or complexly' aggregated crystals.

ince horas: solutions are sufliciently alkaline to saponify fatty acids, I have found it more convenient to add the soap in the form of a fatty acid. Oleic acid being liquid at ordfnary temperature has been foundlnost convenient although other fatty acids, or llllX- Lures thereof have been found just as silicacious for the purpose of my invention. From one-half to one pint of oleic acid is suliicient to suppress aggregation in a batch of 2500 7 gallons, that is, from one to two volumes of si red that the seed formed at the'beginning.

be of simple single structure. It is di'lficult to produce a single crystal product from aggregated seed. \Vhile it is possible to add the colloid or its essence, such as oleic acid, to

' the hot batch of liquor as its enters the cooler,

I have found it preferable to add it as near the point of crystal inception as practicable. It is well known that soap solutions undergo certain physical or chemical changes upon standing, commonly known as ageing. I have found that the freshly prepared agent is'considerably superior to one that has undergone ageing. In order to gain the maximum effect I prefer to add oleic acid to the liquor immediately prior to crystallization. However where conditions have made this method im practicable, satisfactory results have been ob tained by adding the emulsion colloid or itsprevious to the start of cryst'tially only borax on coolin'gflwhichwprocess j comprises, bringing the solution ofboraxto "aconcentration of bora'x and temperature at -which' 't'l1e' "solution is near theus atu'ration point with respect to the thorax, adding a essence sometime tallization. v

While I have described the precipitating process as carried out by cooling the solutions by vacuum or by vaporization of water content produced by rcduction of pressure, I have found that any other convenient method of rapid cooling, such as the use of cooling coils, is effective f-or'the purposesof this invention.

While there has been herein described a particular form or example of a process em bodying the inventiomwell suited for carry ing out the objects-of the invention, 1t is to be understood that the process is notnecessarily limited to the specific example given, but includes all such modifications and changes as come within the scope of the append claims.

I claim: a p v 1. A process of crystallizingborax from aqueoussolutions which reclpltate substantially only borax on coo 1n g whlclr process comprises, adding an emulsion colloid to the solution and cooling the solution while agitating the same to precipitate borax, the emulsion colloid added being the type adapted to prevent aggregation of the crystals of borax precipitated.

ii-pleases of:-crystallizing borax from aqueous solutions which precipitate substantially only borax on-coolingwhich process comprises, addingtothe solution a quantity 'ofemulsion colloid, cooling the solution and agitating the solution to precipitate 'TlQOIEtX crystals, the emulsion colloid added being of the typeadapted to prevent aggregation of the crystals of borax precipitated, the -precipitationbeing accelerated: by the additionpi s'eedcrystalsof borair. 1

3. A process of crystallizingborax from aqueous solutions which "comprises; adding soap tothe solution prior to crystallization, and bringing the solution to suflicientlylow temperature as to permit the precipitation of the tibia); crystals, the soapoperating to prevent aggregation: ofthe crystals of borax precipitated. 1 a

4. A -process'ofcrystallizing boraxfrom aqiieous solutions which comprises, adding to; the solution soap, adding seed crystals of bot-ax, and reducing the ten'lpe'ratur-e of the solution sufficiently to effect precipitationof borax crystalgthe soap operating to prevent, aggregation of thecrystalsw 5 if-A process of 'crystallizingborax-froin aqueous solutions which precipitate. substantially only borax' on cooling which process comprises, bringing the solution to a temperature andconc'entration at which the solution is near the saturation point with respect to boraX; adding a solution .of .sapon'ifiabl'e 'materi'altothe' solution and cooling the solution to effect; precipitation of crystals of borax, the saponifia'ble material operating to prevent aggregation of thecrystalss 6. process of crystallizing borax' from aqueous solutions which precipitate substansaponifiable material-to the "solution and *quicklytooling the solution to efi ect precipitation'yof the bo'raigtfthe saponifiable mate- "rial operating to prevent"aggregationo'fthe borax crystals.

7 A process o'f crystallizing boran from aqueous solutions which precipitate substantially only borax on cooling which process comprises, adding an emulsion colloid to the 3 solution prior to crystallizationin sufiicient -1 quantity to prevent aggregation of borax crystals upon subsequent precipitation, andrapidly cooling the solution while agitating the same to precipitate the borax crystals.

8. A process of crystallizing b'orax from aqueous solutions in which oleic acid is added to produce a product consisting essentially of single crystals;

9. A process of crystallizing borax from aqueous solutions which precipitate substantially only borax on cooling which process comprises, adding an emulsion colloid to the solution in suflicient quantities to prevent aggregation of borax crystals when precipitating, then reducingthe pressure on said solution in order to rapidly cool the solution, thereby precipitating borax crystals essentially as single crystals.

10. A process of crystallizingloorax from aqueous solutions which precipitate substantially only borax on cooling which process comprises, adding an emulsion colloid to the solution in sufiicient quantities to prevent aggregation of horax crystals when precipitating, then reducing the pressure on said solution in order. to rapidly cool thesolution, thereby precipitating borax crystals essentially as: single crystals, and agitating the solution during the cooling effected by pressure reduction. 1

11. A process of crystallizing borax from aqueous solutions which precipitate substantially only borax on cooling which process comprises, adding an emulsion colloid to the solution in sufficient quantities to prevent aggregation of borax crystals when precipitating, then reducing the pressure on said solution in order to rapidly cool the solution, thereby precipitating borax crystals essentially as single crystals, and adding seed crystals to accelerate precipitation of the borax.

12. A process of crystallizing borax from aqueous solutionswhich precipitate substantially only borax on cooling which process comprises, adding an emulsion colloid to the solution in sufficient quantities to prevent aggregation of horax crystals when precipitating, then tion in order to rapidly cool the solution, thereby precipitating borax crystals essentially as single crystals, agitating the solution during cooling and adding seed crystals to facilitate the precipitation of boraX.

Signed at Trona, California, this 8th day of April, 1929.

ROBERT B. FEET.

reducing the pressure on said solu- 

